The present invention can find most utility when applied for shock absorbers in safety belts of builders, erectors, mountaineers, as well as for automobile safety seat belts, that is, in the protection (safety) systems, wherein necessity arises under certain operating conditions to absorb excess kinetic energy at a level not exceeding maximum admissible values.
At present a great many types of devices for absorbing impact effect of kinetic energy are known to be in current use in the above-mentioned safety engineering means. The most promising is the application in such means the shock absorbing devices based on the various textile materials, whose action is relied upon plastic deformation of a single or several system of filament fibres, since the operation threshold and reliability of such devices are less subject to the effect of such factors as cold, heat, water, dust and dirt than, e.g., those in the friction-type devices, which enables the former shock absorbing devices to be regarded as versatile ones.
Known in the present state of the art is the construction of an automobile safety seat belt incorporating an additional damping device. The device consists of a load-carrying textile band or ribbon folded into a loop and stitched across with sewing threads. The thus-stitched-up loop is pressed against one of the ends of the band load-carrying portion and a sleeve is fitted onto the loop and the band end. Then one of the ends of the band load-carrying portion is held in the car body, and the other end, to the band of the safety seat belt. Once the load applied to the safety seat belt has exceeded the operation threshold of the damping device, first the sleeve is liable to destruct, then the sewing thread stitches do so, thus ensuring energy absorption.
The aforementioned damping device is disadvantageous in the technique of joining the load-carrying band with sewing threads to obtain a loop. The thread stitches should be arranged strictly square with the warp threads of the band and with the direction of load application, since even minute skews, which are practically inescapable, affect badly the possibility of simultaneous tearing-down of the sewing threads throughout the entire stitch length. This, in turn, might result in an uniform operation threshold of the device and hence in affected operational reliability of the shock absorber. Moreover, as practice has demonstrated that, when using textile bands 30 to 40 mm wide made from textile fibres having an ultimate breaking strength of from 65 to 70 gf/tex, it is difficult to produce damping devices featuring the operation threshold in excess of 200 kgf. It is likewise impossible in the known device to carry out a reliable nondestructive check for quality of sewing joint, which affects adversely the reliability of the device as well.
One more device for damping impact loads in a safety system is known in the art, comprising a flexible band having two vacant ends and made up of two layers formed due to its folding, said band being associated with an energy-absorbing means. The energy-absorbing means is made as a strap composed of two bands bonded together. One of the flexible band ends is connected to the car body, while the other end is associated to a bracket, which is likewise held to the car body. The bracket carries also a reel for one of the ends of the safety seat belt band to retain and wind up. In the case of an abrupt loading of the safety seat belt the reel provided with retainers, wedges up the band, thus preventing it from unreeling. As soon as a preset load is attained the bracket along with the reel is detached from the car body, whereupon the strap of the flexible band starts taking up load. As a result, the strap begins to split into two portions at a preset load and thus absorbing surplus kinetic energy.
However, it happens rather difficult to retain the operation threshold after a prolonged period of operation under diverse atmospheric conditions. Besides, the known device likewise offers no possibility of carrying out a nondestructive reliable check for quality of bonded joints both at the stage of production and under in-service conditions, which affects adversely the reliability of the device.
It is therefore a primary and essential object of the present invention to eliminate the disadvantages mentioned above, from which the aforediscussed devices for damping impact load suffer.